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Papers by Dennis Helfritch

Journal of Bacteriology & Parasitology, Jan 14, 2014

Practical Cold Spray

In accordance with application, development, and standardization needs, in this chapter, the stan... more In accordance with application, development, and standardization needs, in this chapter, the standards that are developed for cold spray and directly applicable to cold spray are highlighted. A pathway is presented for developing cold spray procedures and writing new standards for applications that don’t follow an available guide or a standard. Furthermore, destructive and nondestructive testing methods are presented for product qualification and certification phases. The listed nondestructive methods are also applicable to evaluate the structural and operational integrity of cold spray manufactured products that are in service.

Practical Cold Spray, 2021

Practical Cold Spray, 2021

Practical Cold Spray, 2021

Chapter 3 describes the basic cold spray system configuration, along with the integration of auxi... more Chapter 3 describes the basic cold spray system configuration, along with the integration of auxiliary equipment. A step-by-step process to properly set up a basic cold spray facility, including the required footprint, gas supply, safety precautions, and other important considerations, is outlined. On-site support infrastructure and commercially available equipment are described.

US utilities are faced with new economic challenges to remain competitive in light of deregulatio... more US utilities are faced with new economic challenges to remain competitive in light of deregulation initiatives. In addition, environmental pressures are forcing many of these utilities to be prepared to reduce air emissions such as mercury vapor and fine particulates from coal-burning plants. The technology described here employs a circulating fluid bed of fly ash to achieve a high particle density. Activated carbon injected into the circulating ash bed adsorbs mercury vapor, due to its high residence time in the recirculating bed. This allows very effective utilization of the carbon. Fine particles entering the system are formed into larger agglomerates through collision with the bed particles. A conventional electrostatic precipitator can then readily capture the larger particles leaving the bed. This technology was pilot tested for a three-month period on a slipstream of gas exiting a coal-fired boiler at PSE and G's Mercer Generating Station. The results show that mercury va...

Description/Abstract A solid-state electrochemical process now in an early stage of development c... more Description/Abstract A solid-state electrochemical process now in an early stage of development converts NO {sub x} and SO {sub x} to nitrogen, oxygen, and sulfur. Process objectives are to remove 90+% of SO {sub x} and NO {sub x} and 99% of particulates from ...

International Thermal Spray Conference

The importance of high velocity for good particle deposition efficiency in the cold spray process... more The importance of high velocity for good particle deposition efficiency in the cold spray process is well known. Small particles achieve high velocities during nozzle acceleration, but also decelerate rapidly in the flow downstream of the bow shock wave. This study examines the effect of particle size on velocity and deposition efficiency in the cold spray process by means of flow modeling and gas-particle dynamics. Particle trajectories are modeled from the nozzle chamber to the impact with the substrate. Optimum particle size is identified for various particle characteristics and spray configurations.

Coatings

Bacterial and viral contamination of contact surfaces increases the risk of infection. A great de... more Bacterial and viral contamination of contact surfaces increases the risk of infection. A great deal of work has been done on the capabilities of copper and its alloys to protect against a variety of microorganisms endangering public health, particularly in healthcare and food processing applications. This work has conclusively shown the effectiveness of copper for touch surface disinfection; however, the optimum microstructural characteristics of the copper surface have not been established. The sterilization effectiveness of three kinetically sprayed copper surfaces and two copper feedstocks were examined. The surfaces were inoculated with methicillin-resistant Staphylococcus aureus (MRSA) and influenza A virus. After a two-hour exposure to the surfaces, the surviving microorganisms were assayed, and the results contrasted. These tests showed substantial antimicrobial differences between the coatings generated by the spray techniques and those obtained by different feedstock powder...

Journal of Thermal Spray Technology, 2016

ABSTRACT The results of the pilot scale testing and of the economic evaluation are: SOâ removal i... more ABSTRACT The results of the pilot scale testing and of the economic evaluation are: SOâ removal is greater than 90% and is relatively independent of beam energy. For high sulfur coal, operation of the electron beam allows the lime usage to be reduced by 33%. NO/sub x/ removal occurs almost entirely in the electron beam reaction area and is strongly dependent on radiation dose and SOâ concentration. For high sulfur coal, 80% NO/sub x/ removal can be achieved at 1.5 Mrad, 90% at 2.0 Mrad. Using solids generated by another pilot scale spray dryer system, it was demonstrated that by the addition of water these solids could be stabilized to an impermeable solid capable of permanently containing nitrates. The cost of an electron beam, spray dryer, fabric filter system for a new, 500 MW pulverized coal fueled, generating station is 224MMforlowsulfurcoaland224 MM for low sulfur coal and 224MMforlowsulfurcoaland210 MM for high sulfur coal. The 30 year levelized revenue requirements are 25.1 and 28.5 mill/kWh, respectively. These economic results compare favorably with alternate control technology.

Radiat Phys Chem, 1984

This study examines the feasibility of adding an electron beam between the spray dryer and the fa... more This study examines the feasibility of adding an electron beam between the spray dryer and the fabric filter of "dry scrubber" flue gas desulfurization ~FGD) systems. The beam promises effective removal of nitrogen oxides (NOx) and sulfur dioxide (S02) , even at higher coal-sulfur levels than usually economic for dry scrubbers. The beam excites gas molecules, promoting reactions that convert SO 2 and NO x to acids that then react with calcium compounds and are removed by the filter. The cost findings are promising for both manufacture and operation. The system uses commercially available components. The relatively low temperatures and high humidity downstream of the spray dryer favor economic beam operation. The beam removes S02, so the dryer can be run for economy, not high removal. Pilot scale tests will soon be carried out which are designed to verify earlier bench scale test results and to serve as the next step to full commercialization. It is expected that better than 90% SO 2 and NO x removal will be achieved.

Journal of Bacteriology & Parasitology, Jan 14, 2014

Practical Cold Spray

In accordance with application, development, and standardization needs, in this chapter, the stan... more In accordance with application, development, and standardization needs, in this chapter, the standards that are developed for cold spray and directly applicable to cold spray are highlighted. A pathway is presented for developing cold spray procedures and writing new standards for applications that don’t follow an available guide or a standard. Furthermore, destructive and nondestructive testing methods are presented for product qualification and certification phases. The listed nondestructive methods are also applicable to evaluate the structural and operational integrity of cold spray manufactured products that are in service.

Practical Cold Spray, 2021

Practical Cold Spray, 2021

Practical Cold Spray, 2021

Chapter 3 describes the basic cold spray system configuration, along with the integration of auxi... more Chapter 3 describes the basic cold spray system configuration, along with the integration of auxiliary equipment. A step-by-step process to properly set up a basic cold spray facility, including the required footprint, gas supply, safety precautions, and other important considerations, is outlined. On-site support infrastructure and commercially available equipment are described.

US utilities are faced with new economic challenges to remain competitive in light of deregulatio... more US utilities are faced with new economic challenges to remain competitive in light of deregulation initiatives. In addition, environmental pressures are forcing many of these utilities to be prepared to reduce air emissions such as mercury vapor and fine particulates from coal-burning plants. The technology described here employs a circulating fluid bed of fly ash to achieve a high particle density. Activated carbon injected into the circulating ash bed adsorbs mercury vapor, due to its high residence time in the recirculating bed. This allows very effective utilization of the carbon. Fine particles entering the system are formed into larger agglomerates through collision with the bed particles. A conventional electrostatic precipitator can then readily capture the larger particles leaving the bed. This technology was pilot tested for a three-month period on a slipstream of gas exiting a coal-fired boiler at PSE and G's Mercer Generating Station. The results show that mercury va...

Description/Abstract A solid-state electrochemical process now in an early stage of development c... more Description/Abstract A solid-state electrochemical process now in an early stage of development converts NO {sub x} and SO {sub x} to nitrogen, oxygen, and sulfur. Process objectives are to remove 90+% of SO {sub x} and NO {sub x} and 99% of particulates from ...

International Thermal Spray Conference

The importance of high velocity for good particle deposition efficiency in the cold spray process... more The importance of high velocity for good particle deposition efficiency in the cold spray process is well known. Small particles achieve high velocities during nozzle acceleration, but also decelerate rapidly in the flow downstream of the bow shock wave. This study examines the effect of particle size on velocity and deposition efficiency in the cold spray process by means of flow modeling and gas-particle dynamics. Particle trajectories are modeled from the nozzle chamber to the impact with the substrate. Optimum particle size is identified for various particle characteristics and spray configurations.

Coatings

Bacterial and viral contamination of contact surfaces increases the risk of infection. A great de... more Bacterial and viral contamination of contact surfaces increases the risk of infection. A great deal of work has been done on the capabilities of copper and its alloys to protect against a variety of microorganisms endangering public health, particularly in healthcare and food processing applications. This work has conclusively shown the effectiveness of copper for touch surface disinfection; however, the optimum microstructural characteristics of the copper surface have not been established. The sterilization effectiveness of three kinetically sprayed copper surfaces and two copper feedstocks were examined. The surfaces were inoculated with methicillin-resistant Staphylococcus aureus (MRSA) and influenza A virus. After a two-hour exposure to the surfaces, the surviving microorganisms were assayed, and the results contrasted. These tests showed substantial antimicrobial differences between the coatings generated by the spray techniques and those obtained by different feedstock powder...

Journal of Thermal Spray Technology, 2016

ABSTRACT The results of the pilot scale testing and of the economic evaluation are: SOâ removal i... more ABSTRACT The results of the pilot scale testing and of the economic evaluation are: SOâ removal is greater than 90% and is relatively independent of beam energy. For high sulfur coal, operation of the electron beam allows the lime usage to be reduced by 33%. NO/sub x/ removal occurs almost entirely in the electron beam reaction area and is strongly dependent on radiation dose and SOâ concentration. For high sulfur coal, 80% NO/sub x/ removal can be achieved at 1.5 Mrad, 90% at 2.0 Mrad. Using solids generated by another pilot scale spray dryer system, it was demonstrated that by the addition of water these solids could be stabilized to an impermeable solid capable of permanently containing nitrates. The cost of an electron beam, spray dryer, fabric filter system for a new, 500 MW pulverized coal fueled, generating station is 224MMforlowsulfurcoaland224 MM for low sulfur coal and 224MMforlowsulfurcoaland210 MM for high sulfur coal. The 30 year levelized revenue requirements are 25.1 and 28.5 mill/kWh, respectively. These economic results compare favorably with alternate control technology.

Radiat Phys Chem, 1984

This study examines the feasibility of adding an electron beam between the spray dryer and the fa... more This study examines the feasibility of adding an electron beam between the spray dryer and the fabric filter of "dry scrubber" flue gas desulfurization ~FGD) systems. The beam promises effective removal of nitrogen oxides (NOx) and sulfur dioxide (S02) , even at higher coal-sulfur levels than usually economic for dry scrubbers. The beam excites gas molecules, promoting reactions that convert SO 2 and NO x to acids that then react with calcium compounds and are removed by the filter. The cost findings are promising for both manufacture and operation. The system uses commercially available components. The relatively low temperatures and high humidity downstream of the spray dryer favor economic beam operation. The beam removes S02, so the dryer can be run for economy, not high removal. Pilot scale tests will soon be carried out which are designed to verify earlier bench scale test results and to serve as the next step to full commercialization. It is expected that better than 90% SO 2 and NO x removal will be achieved.